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<span id="Identifiers"></span><h3 class="section">4.3 Identifiers</h3>

<ul>
<li> <cite>Which additional multibyte characters may appear in identifiers
and their correspondence to universal character names (C99 and C11 6.4.2).</cite>

<p>See <a href="https://gcc.gnu.org/onlinedocs/cpp/Implementation_002ddefined-behavior.html#Implementation_002ddefined-behavior">Implementation-defined
behavior</a> in <cite>The C Preprocessor</cite>.
</p>
</li><li> <cite>The number of significant initial characters in an identifier
(C90 6.1.2, C90, C99 and C11 5.2.4.1, C99 and C11 6.4.2).</cite>

<p>For internal names, all characters are significant.  For external names,
the number of significant characters are defined by the linker; for
almost all targets, all characters are significant.
</p>
</li><li> <cite>Whether case distinctions are significant in an identifier with
external linkage (C90 6.1.2).</cite>

<p>This is a property of the linker.  C99 and C11 require that case distinctions
are always significant in identifiers with external linkage and
systems without this property are not supported by GCC.
</p>
</li></ul>




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